The US military is keeping its "options" open as its warships track Iranian vessels suspected of carrying weapons for Huthi rebels in Yemen, officials said Tuesday.

The aircraft carrier USS Theodore Roosevelt and escort ships have deployed to waters off of Yemen "in response to the deteriorating security situation in Yemen," Pentagon spokesman Colonel Steven Warren told reporters.

Warren said the American warships are closely monitoring a convoy of nine Iranian cargo ships in the area but would not say whether the US naval forces might try to intercept the convoy if it approached a Yemeni port.

"We don't know what the Iranian convoy of ships plans to do, but we are watching them," Warren said. "By having American sea power in the region, we preserve our options."

There had been no communication so far with the Iranian ships, he said.

But he said some media reporting on the situation, which suggested the Americans were preparing to prevent the Iranian convoy from reaching Yemen if there were weapons on board the ships, was "a bit over-cranked."

The presence of the Iranian convoy "is one of the factors" in the US naval deployment but not the only one, he added.

A total of 12 US ships were in the region stretching from the Red Sea to the Gulf of Aden and the Arabian Sea, including nine combat vessels, navy officers said.

The warships included the Roosevelt, with a crew of about 5,000 and some 60 aircraft, a group of three amphibious ships and two minesweepers. Three resupply ships are in the area to support combat vessels.

"They are operating in the Arabian Sea and the Gulf of Aden with the very clear mission to ensure that shipping lanes remain open, to ensure there's freedom of navigation through those critical waterways and to ensure there's maritime security," Warren said.

US defense officials told AFP on Monday that the Iranian vessels were suspected of carrying arms and equipment destined for the Huthi rebels. But the officials suggested it was more likely that Saudi Arabia, Egypt or their allies take action to intercept the Iranian ships if necessary.

The UN Security Council earlier this month imposed an arms embargo on the Iranian-backed Huthi forces in Yemen.

The United States says it is not taking part in direct military action against the Huthi rebels and instead is providing intelligence and logistical support, including aerial refueling, for Saudi-led air strikes against the rebels.

The Saudi-led intervention was launched in late March in a bid to help pro-government forces fighting the Iranian-backed Huthi rebels.

Yemen was plunged into chaos last year when the Huthis seized the capital Sanaa.